mpu9250

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MPU9255.h

00001 #ifndef MPU9255_H
00002 #define MPU9255_H
00003  
00004 #include "mbed.h"
00005 #include "math.h"
00006  
00007 // See also MPU-9255 Register Map and Descriptions, Revision 4.0, RM-MPU-9255A-00, Rev. 1.4, 9/9/2013 for registers not listed in 
00008 // above document; the MPU9255 and MPU9150 are virtually identical but the latter has a different register map
00009 //
00010 //Magnetometer Registers
00011 #define AK8963_ADDRESS   0x0C<<1
00012 #define AK8963_WHO_AM_I  0x00 // should return 0x48
00013 #define AK8963_INFO      0x01
00014 #define AK8963_ST1       0x02  // data ready status bit 0
00015 #define AK8963_XOUT_L    0x03  // data
00016 #define AK8963_XOUT_H    0x04
00017 #define AK8963_YOUT_L    0x05
00018 #define AK8963_YOUT_H    0x06
00019 #define AK8963_ZOUT_L    0x07
00020 #define AK8963_ZOUT_H    0x08
00021 #define AK8963_ST2       0x09  // Data overflow bit 3 and data read error status bit 2
00022 #define AK8963_CNTL1     0x0A  // Power down (0000), single-measurement (0001), self-test (1000) and Fuse ROM (1111) modes on bits 3:0
00023 #define AK8963_CNTL2     0x0B  // Soft reset: Normal(0000), Rest(0001)
00024 #define AK8963_ASTC      0x0C  // Self test control
00025 #define AK8963_I2CDIS    0x0F  // I2C disable(00011011)
00026 #define AK8963_ASAX      0x10  // Fuse ROM x-axis sensitivity adjustment value
00027 #define AK8963_ASAY      0x11  // Fuse ROM y-axis sensitivity adjustment value
00028 #define AK8963_ASAZ      0x12  // Fuse ROM z-axis sensitivity adjustment value
00029 
00030 #define SELF_TEST_X_GYRO 0x00                  
00031 #define SELF_TEST_Y_GYRO 0x01                                                                          
00032 #define SELF_TEST_Z_GYRO 0x02
00033 
00034 /*#define X_FINE_GAIN      0x03 // [7:0] fine gain
00035 #define Y_FINE_GAIN      0x04
00036 #define Z_FINE_GAIN      0x05
00037 #define XA_OFFSET_H      0x06 // User-defined trim values for accelerometer
00038 #define XA_OFFSET_L_TC   0x07
00039 #define YA_OFFSET_H      0x08
00040 #define YA_OFFSET_L_TC   0x09
00041 #define ZA_OFFSET_H      0x0A
00042 #define ZA_OFFSET_L_TC   0x0B */
00043 
00044 #define SELF_TEST_X_ACCEL 0x0D
00045 #define SELF_TEST_Y_ACCEL 0x0E    
00046 #define SELF_TEST_Z_ACCEL 0x0F
00047 
00048 #define SELF_TEST_A      0x10
00049 
00050 #define XG_OFFSET_H      0x13  // User-defined trim values for gyroscope
00051 #define XG_OFFSET_L      0x14
00052 #define YG_OFFSET_H      0x15
00053 #define YG_OFFSET_L      0x16
00054 #define ZG_OFFSET_H      0x17
00055 #define ZG_OFFSET_L      0x18
00056 #define SMPLRT_DIV       0x19
00057 #define CONFIG           0x1A
00058 #define GYRO_CONFIG      0x1B
00059 #define ACCEL_CONFIG     0x1C
00060 #define ACCEL_CONFIG2    0x1D
00061 #define LP_ACCEL_ODR     0x1E   
00062 #define WOM_THR          0x1F   
00063 
00064 #define MOT_DUR          0x20  // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms
00065 #define ZMOT_THR         0x21  // Zero-motion detection threshold bits [7:0]
00066 #define ZRMOT_DUR        0x22  // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms
00067 
00068 #define FIFO_EN          0x23
00069 #define I2C_MST_CTRL     0x24   
00070 #define I2C_SLV0_ADDR    0x25
00071 #define I2C_SLV0_REG     0x26
00072 #define I2C_SLV0_CTRL    0x27
00073 #define I2C_SLV1_ADDR    0x28
00074 #define I2C_SLV1_REG     0x29
00075 #define I2C_SLV1_CTRL    0x2A
00076 #define I2C_SLV2_ADDR    0x2B
00077 #define I2C_SLV2_REG     0x2C
00078 #define I2C_SLV2_CTRL    0x2D
00079 #define I2C_SLV3_ADDR    0x2E
00080 #define I2C_SLV3_REG     0x2F
00081 #define I2C_SLV3_CTRL    0x30
00082 #define I2C_SLV4_ADDR    0x31
00083 #define I2C_SLV4_REG     0x32
00084 #define I2C_SLV4_DO      0x33
00085 #define I2C_SLV4_CTRL    0x34
00086 #define I2C_SLV4_DI      0x35
00087 #define I2C_MST_STATUS   0x36
00088 #define INT_PIN_CFG      0x37
00089 #define INT_ENABLE       0x38
00090 #define DMP_INT_STATUS   0x39  // Check DMP interrupt
00091 #define INT_STATUS       0x3A
00092 #define ACCEL_XOUT_H     0x3B
00093 #define ACCEL_XOUT_L     0x3C
00094 #define ACCEL_YOUT_H     0x3D
00095 #define ACCEL_YOUT_L     0x3E
00096 #define ACCEL_ZOUT_H     0x3F
00097 #define ACCEL_ZOUT_L     0x40
00098 #define TEMP_OUT_H       0x41
00099 #define TEMP_OUT_L       0x42
00100 #define GYRO_XOUT_H      0x43
00101 #define GYRO_XOUT_L      0x44
00102 #define GYRO_YOUT_H      0x45
00103 #define GYRO_YOUT_L      0x46
00104 #define GYRO_ZOUT_H      0x47
00105 #define GYRO_ZOUT_L      0x48
00106 #define EXT_SENS_DATA_00 0x49
00107 #define EXT_SENS_DATA_01 0x4A
00108 #define EXT_SENS_DATA_02 0x4B
00109 #define EXT_SENS_DATA_03 0x4C
00110 #define EXT_SENS_DATA_04 0x4D
00111 #define EXT_SENS_DATA_05 0x4E
00112 #define EXT_SENS_DATA_06 0x4F
00113 #define EXT_SENS_DATA_07 0x50
00114 #define EXT_SENS_DATA_08 0x51
00115 #define EXT_SENS_DATA_09 0x52
00116 #define EXT_SENS_DATA_10 0x53
00117 #define EXT_SENS_DATA_11 0x54
00118 #define EXT_SENS_DATA_12 0x55
00119 #define EXT_SENS_DATA_13 0x56
00120 #define EXT_SENS_DATA_14 0x57
00121 #define EXT_SENS_DATA_15 0x58
00122 #define EXT_SENS_DATA_16 0x59
00123 #define EXT_SENS_DATA_17 0x5A
00124 #define EXT_SENS_DATA_18 0x5B
00125 #define EXT_SENS_DATA_19 0x5C
00126 #define EXT_SENS_DATA_20 0x5D
00127 #define EXT_SENS_DATA_21 0x5E
00128 #define EXT_SENS_DATA_22 0x5F
00129 #define EXT_SENS_DATA_23 0x60
00130 #define MOT_DETECT_STATUS 0x61
00131 #define I2C_SLV0_DO      0x63
00132 #define I2C_SLV1_DO      0x64
00133 #define I2C_SLV2_DO      0x65
00134 #define I2C_SLV3_DO      0x66
00135 #define I2C_MST_wait_ms_CTRL 0x67
00136 #define SIGNAL_PATH_RESET  0x68
00137 #define MOT_DETECT_CTRL  0x69
00138 #define USER_CTRL        0x6A  // Bit 7 enable DMP, bit 3 reset DMP
00139 #define PWR_MGMT_1       0x6B // Device defaults to the SLEEP mode
00140 #define PWR_MGMT_2       0x6C
00141 #define DMP_BANK         0x6D  // Activates a specific bank in the DMP
00142 #define DMP_RW_PNT       0x6E  // Set read/write pointer to a specific start address in specified DMP bank
00143 #define DMP_REG          0x6F  // Register in DMP from which to read or to which to write
00144 #define DMP_REG_1        0x70
00145 #define DMP_REG_2        0x71 
00146 #define FIFO_COUNTH      0x72
00147 #define FIFO_COUNTL      0x73
00148 #define FIFO_R_W         0x74
00149 #define WHO_AM_I_MPU9255 0x75 // Should return 0x71
00150 #define XA_OFFSET_H      0x77
00151 #define XA_OFFSET_L      0x78
00152 #define YA_OFFSET_H      0x7A
00153 #define YA_OFFSET_L      0x7B
00154 #define ZA_OFFSET_H      0x7D
00155 #define ZA_OFFSET_L      0x7E
00156 
00157 // Using the MSENSR-9255 breakout board, ADO is set to 0 
00158 // Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1
00159 //mbed uses the eight-bit device address, so shift seven-bit addresses left by one!
00160 #define ADO 0
00161 #if ADO
00162 #define MPU9255_ADDRESS 0x69<<1  // Device address when ADO = 1
00163 #else
00164 #define MPU9255_ADDRESS 0x68<<1  // Device address when ADO = 0
00165 #endif  
00166 
00167 // Set initial input parameters
00168 enum Ascale {
00169   AFS_2G = 0,
00170   AFS_4G,
00171   AFS_8G,
00172   AFS_16G
00173 };
00174 
00175 enum Gscale {
00176   GFS_250DPS = 0,
00177   GFS_500DPS,
00178   GFS_1000DPS,
00179   GFS_2000DPS
00180 };
00181 
00182 enum Mscale {
00183   MFS_14BITS = 0, // 0.6 mG per LSB
00184   MFS_16BITS      // 0.15 mG per LSB
00185 };
00186 
00187 uint8_t Ascale = AFS_2G;     // AFS_2G, AFS_4G, AFS_8G, AFS_16G
00188 uint8_t Gscale = GFS_250DPS; // GFS_250DPS, GFS_500DPS, GFS_1000DPS, GFS_2000DPS
00189 uint8_t Mscale = MFS_16BITS; // MFS_14BITS or MFS_16BITS, 14-bit or 16-bit magnetometer resolution
00190 uint8_t Mmode = 0x06;        // Either 8 Hz 0x02) or 100 Hz (0x06) magnetometer data ODR  
00191 float aRes, gRes, mRes;      // scale resolutions per LSB for the sensors
00192 
00193 //Set up I2C, (SDA,SCL)
00194 I2C i2c(PB_9, PB_8);
00195 
00196 DigitalOut myled(LED1);
00197     
00198 // Pin definitions
00199 int intPin = 12;  // These can be changed, 2 and 3 are the Arduinos ext int pins
00200 
00201 int16_t accelCount[3];  // Stores the 16-bit signed accelerometer sensor output
00202 int16_t gyroCount[3];   // Stores the 16-bit signed gyro sensor output
00203 int16_t magCount[3];    // Stores the 16-bit signed magnetometer sensor output
00204 float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0};  // Factory mag calibration and mag bias
00205 float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0}; // Bias corrections for gyro and accelerometer
00206 float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values 
00207 int16_t tempCount;   // Stores the real internal chip temperature in degrees Celsius
00208 float temperature;
00209 float SelfTest[6];
00210 
00211 int delt_t = 0; // used to control display output rate
00212 int count_display = 0;  // used to control display output rate
00213 
00214 // parameters for 6 DoF sensor fusion calculations
00215 float PI = 3.14159265358979323846f;
00216 float GyroMeasError = PI * (60.0f / 180.0f);     // gyroscope measurement error in rads/s (start at 60 deg/s), then reduce after ~10 s to 3
00217 float beta = sqrt(3.0f / 4.0f) * GyroMeasError;  // compute beta
00218 float GyroMeasDrift = PI * (1.0f / 180.0f);      // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s)
00219 float zeta = sqrt(3.0f / 4.0f) * GyroMeasDrift;  // compute zeta, the other free parameter in the Madgwick scheme usually set to a small or zero value
00220 #define Kp 2.0f * 5.0f // these are the free parameters in the Mahony filter and fusion scheme, Kp for proportional feedback, Ki for integral
00221 #define Ki 0.0f
00222 
00223 float pitch, yaw, roll;
00224 float deltat = 0.0f;                             // integration interval for both filter schemes
00225 int lastUpdate = 0, firstUpdate = 0, Now = 0;    // used to calculate integration interval                               // used to calculate integration interval
00226 float q[4] = {1.0f, 0.0f, 0.0f, 0.0f};
00227 //float q[4] = {1.0f, 0.0f, 0.0f, 0.0f};           // vector to hold quaternion
00228 float eInt[3] = {0.0f, 0.0f, 0.0f};              // vector to hold integral error for Mahony method
00229 
00230 class MPU9255 {
00231  
00232     protected:
00233  
00234     public:
00235   //===================================================================================================================
00236 //====== Set of useful function to access acceleratio, gyroscope, and temperature data
00237 //===================================================================================================================
00238 
00239     void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
00240 {
00241    char data_write[2];
00242    data_write[0] = subAddress;
00243    data_write[1] = data;
00244    i2c.write(address, data_write, 2, 0);
00245 }
00246 
00247     char readByte(uint8_t address, uint8_t subAddress)
00248 {
00249     char data[1]; // `data` will store the register data     
00250     char data_write[1];
00251     data_write[0] = subAddress;
00252     i2c.write(address, data_write, 1, 1); // no stop
00253     i2c.read(address, data, 1, 0); 
00254     return data[0]; 
00255 }
00256 
00257     void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
00258 {     
00259     char data[14];
00260     char data_write[1];
00261     data_write[0] = subAddress;
00262     i2c.write(address, data_write, 1, 1); // no stop
00263     i2c.read(address, data, count, 0); 
00264     for(int ii = 0; ii < count; ii++) {
00265      dest[ii] = data[ii];
00266     }
00267 } 
00268  
00269 
00270 void getMres() {
00271   switch (Mscale)
00272   {
00273     // Possible magnetometer scales (and their register bit settings) are:
00274     // 14 bit resolution (0) and 16 bit resolution (1)
00275     case MFS_14BITS:
00276           mRes = 10.0*4912.0/8190.0; // Proper scale to return milliGauss
00277           break;
00278     case MFS_16BITS:
00279           mRes = 10.0*4912.0/32760.0; // Proper scale to return milliGauss
00280           break;
00281   }
00282 }
00283 
00284 
00285 void getGres() {
00286   switch (Gscale)
00287   {
00288     // Possible gyro scales (and their register bit settings) are:
00289     // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11). 
00290         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00291     case GFS_250DPS:
00292           gRes = 250.0/32768.0;
00293           break;
00294     case GFS_500DPS:
00295           gRes = 500.0/32768.0;
00296           break;
00297     case GFS_1000DPS:
00298           gRes = 1000.0/32768.0;
00299           break;
00300     case GFS_2000DPS:
00301           gRes = 2000.0/32768.0;
00302           break;
00303   }
00304 }
00305 
00306 
00307 void getAres() {
00308   switch (Ascale)
00309   {
00310     // Possible accelerometer scales (and their register bit settings) are:
00311     // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11). 
00312         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00313     case AFS_2G:
00314           aRes = 2.0/32768.0;
00315           break;
00316     case AFS_4G:
00317           aRes = 4.0/32768.0;
00318           break;
00319     case AFS_8G:
00320           aRes = 8.0/32768.0;
00321           break;
00322     case AFS_16G:
00323           aRes = 16.0/32768.0;
00324           break;
00325   }
00326 }
00327 
00328 
00329 void readAccelData(int16_t * destination)
00330 {
00331   uint8_t rawData[6];  // x/y/z accel register data stored here
00332   readBytes(MPU9255_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
00333   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00334   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00335   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00336 }
00337 
00338 void readGyroData(int16_t * destination)
00339 {
00340   uint8_t rawData[6];  // x/y/z gyro register data stored here
00341   readBytes(MPU9255_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
00342   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00343   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00344   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00345 }
00346 
00347 void readMagData(int16_t * destination)
00348 {
00349   uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
00350   if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
00351   readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
00352   uint8_t c = rawData[6]; // End data read by reading ST2 register
00353     if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data
00354     destination[0] = (int16_t)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
00355     destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
00356     destination[2] = (int16_t)(((int16_t)rawData[5] << 8) | rawData[4]) ; 
00357    }
00358   }
00359 }
00360 
00361 int16_t readTempData()
00362 {
00363   uint8_t rawData[2];  // x/y/z gyro register data stored here
00364   readBytes(MPU9255_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array 
00365   return (int16_t)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
00366 }
00367 
00368 
00369 void resetMPU9255() {
00370   // reset device
00371   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00372   wait(0.1);
00373   }
00374   
00375 void resetAK8963() {
00376   // reset device
00377   writeByte(AK8963_ADDRESS, AK8963_CNTL2, 0x0B);
00378   wait(0.1);
00379   }
00380   
00381   void initAK8963(float * destination)
00382 {
00383   // First extract the factory calibration for each magnetometer axis
00384   uint8_t rawData[3];  // x/y/z gyro calibration data stored here
00385   writeByte(AK8963_ADDRESS, AK8963_CNTL1, 0x00); // Power down magnetometer  
00386   wait(0.01);
00387   writeByte(AK8963_ADDRESS, AK8963_CNTL1, 0x0F); // Enter Fuse ROM access mode
00388   wait(0.01);
00389   readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
00390   destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
00391   destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;  
00392   destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f; 
00393   writeByte(AK8963_ADDRESS, AK8963_CNTL1, 0x00); // Power down magnetometer  
00394   wait(0.01);
00395   // Configure the magnetometer for continuous read and highest resolution
00396   // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
00397   // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
00398   writeByte(AK8963_ADDRESS, AK8963_CNTL1, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
00399   wait(0.01);
00400 }
00401 
00402 
00403 void initMPU9255()
00404 {  
00405  // Initialize MPU9255 device
00406  // wake up device
00407   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
00408   wait(0.1); // wait_ms 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt  
00409 
00410  // get stable time source
00411   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00412 
00413  // Configure Gyro and Accelerometer
00414  // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively; 
00415  // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
00416  // Maximum wait_ms is 4.9 ms which is just over a 200 Hz maximum rate
00417   writeByte(MPU9255_ADDRESS, CONFIG, 0x03);  
00418  
00419  // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
00420   writeByte(MPU9255_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; the same rate set in CONFIG above
00421  
00422  // Set gyroscope full scale range
00423  // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
00424   uint8_t c = readByte(MPU9255_ADDRESS, GYRO_CONFIG); // get current GYRO_CONFIG register value
00425  // c = c & ~0xE0; // Clear self-test bits [7:5] 
00426   c = c & ~0x02; // Clear Fchoice bits [1:0] 
00427   c = c & ~0x18; // Clear AFS bits [4:3]
00428   c = c | Gscale << 3; // Set full scale range for the gyro
00429  // c =| 0x00; // Set Fchoice for the gyro to 11 by writing its inverse to bits 1:0 of GYRO_CONFIG
00430   writeByte(MPU9255_ADDRESS, GYRO_CONFIG, c ); // Write new GYRO_CONFIG value to register
00431   
00432  // Set accelerometer full-scale range configuration
00433   c = readByte(MPU9255_ADDRESS, ACCEL_CONFIG); // get current ACCEL_CONFIG register value
00434  // c = c & ~0xE0; // Clear self-test bits [7:5] 
00435   c = c & ~0x18;  // Clear AFS bits [4:3]
00436   c = c | Ascale << 3; // Set full scale range for the accelerometer 
00437   writeByte(MPU9255_ADDRESS, ACCEL_CONFIG, c); // Write new ACCEL_CONFIG register value
00438 
00439  // Set accelerometer sample rate configuration
00440  // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
00441  // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
00442   c = readByte(MPU9255_ADDRESS, ACCEL_CONFIG2); // get current ACCEL_CONFIG2 register value
00443   c = c & ~0x0F; // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
00444   c = c | 0x03;  // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
00445   writeByte(MPU9255_ADDRESS, ACCEL_CONFIG2, c); // Write new ACCEL_CONFIG2 register value
00446 
00447  // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, 
00448  // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting
00449 
00450   // Configure Interrupts and Bypass Enable
00451   // Set interrupt pin active high, push-pull, and clear on read of INT_STATUS, enable I2C_BYPASS_EN so additional chips 
00452   // can join the I2C bus and all can be controlled by the Arduino as master
00453    writeByte(MPU9255_ADDRESS, INT_PIN_CFG, 0x22);    
00454    writeByte(MPU9255_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
00455 }
00456 
00457 // Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
00458 // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
00459 void calibrateMPU9255(float * dest1, float * dest2)
00460 {  
00461   uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
00462   uint16_t ii, packet_count, fifo_count;
00463   int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};
00464   
00465 // reset device, reset all registers, clear gyro and accelerometer bias registers
00466   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00467   wait(0.1);  
00468    
00469 // get stable time source
00470 // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00471   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x01);  
00472   writeByte(MPU9255_ADDRESS, PWR_MGMT_2, 0x00); //all axis(accelerometer & gyro) is on  
00473   wait(0.2);
00474   
00475 // Configure device for bias calculation
00476   writeByte(MPU9255_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
00477   writeByte(MPU9255_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
00478   writeByte(MPU9255_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
00479   writeByte(MPU9255_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
00480   writeByte(MPU9255_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
00481   writeByte(MPU9255_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
00482   wait(0.015);
00483   
00484 // Configure MPU9255 gyro and accelerometer for bias calculation
00485   writeByte(MPU9255_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
00486   writeByte(MPU9255_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
00487   writeByte(MPU9255_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
00488   writeByte(MPU9255_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity
00489  
00490   uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
00491   uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g
00492 
00493 // Configure FIFO to capture accelerometer and gyro data for bias calculation
00494   writeByte(MPU9255_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO  
00495   writeByte(MPU9255_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9255)
00496   wait(0.04); // accumulate 40 samples in 80 milliseconds = 480 bytes
00497 
00498 // At end of sample accumulation, turn off FIFO sensor read
00499   writeByte(MPU9255_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
00500   readBytes(MPU9255_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
00501   fifo_count = ((uint16_t)data[0] << 8) | data[1];
00502   packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging
00503 
00504   for (ii = 0; ii < packet_count; ii++) {
00505     int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
00506     readBytes(MPU9255_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
00507     accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
00508     accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
00509     accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;    
00510     gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
00511     gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
00512     gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;
00513     
00514     accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
00515     accel_bias[1] += (int32_t) accel_temp[1];
00516     accel_bias[2] += (int32_t) accel_temp[2];
00517     gyro_bias[0]  += (int32_t) gyro_temp[0];
00518     gyro_bias[1]  += (int32_t) gyro_temp[1];
00519     gyro_bias[2]  += (int32_t) gyro_temp[2];
00520             
00521 }
00522     accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
00523     accel_bias[1] /= (int32_t) packet_count;
00524     accel_bias[2] /= (int32_t) packet_count;
00525     gyro_bias[0]  /= (int32_t) packet_count;
00526     gyro_bias[1]  /= (int32_t) packet_count;
00527     gyro_bias[2]  /= (int32_t) packet_count;
00528     
00529   if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
00530   else {accel_bias[2] += (int32_t) accelsensitivity;}
00531  
00532 // Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
00533   data[0] = (-gyro_bias[0]/4  >> 8) & 0xFF; // Divide by 4 to get 32.9 LSB per deg/s to conform to expected bias input format
00534   data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
00535   data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
00536   data[3] = (-gyro_bias[1]/4)       & 0xFF;
00537   data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
00538   data[5] = (-gyro_bias[2]/4)       & 0xFF;
00539 
00540 /// Push gyro biases to hardware registers
00541 /*  writeByte(MPU9255_ADDRESS, XG_OFFSET_H, data[0]);
00542   writeByte(MPU9255_ADDRESS, XG_OFFSET_L, data[1]);
00543   writeByte(MPU9255_ADDRESS, YG_OFFSET_H, data[2]);
00544   writeByte(MPU9255_ADDRESS, YG_OFFSET_L, data[3]);
00545   writeByte(MPU9255_ADDRESS, ZG_OFFSET_H, data[4]);
00546   writeByte(MPU9255_ADDRESS, ZG_OFFSET_L, data[5]);
00547 */
00548   dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
00549   dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
00550   dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;
00551 
00552 // Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
00553 // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
00554 // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
00555 // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
00556 // the accelerometer biases calculated above must be divided by 8.
00557 
00558   int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
00559   readBytes(MPU9255_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
00560   accel_bias_reg[0] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00561   readBytes(MPU9255_ADDRESS, YA_OFFSET_H, 2, &data[0]);
00562   accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00563   readBytes(MPU9255_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
00564   accel_bias_reg[2] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00565   
00566   uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
00567   uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis
00568   
00569   for(ii = 0; ii < 3; ii++) {
00570     if(accel_bias_reg[ii] & mask) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
00571   }
00572 
00573   // Construct total accelerometer bias, including calculated average accelerometer bias from above
00574   accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
00575   accel_bias_reg[1] -= (accel_bias[1]/8);
00576   accel_bias_reg[2] -= (accel_bias[2]/8);
00577  
00578   data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
00579   data[1] = (accel_bias_reg[0])      & 0xFF;
00580   data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00581   data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
00582   data[3] = (accel_bias_reg[1])      & 0xFF;
00583   data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00584   data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
00585   data[5] = (accel_bias_reg[2])      & 0xFF;
00586   data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00587 
00588 // Apparently this is not working for the acceleration biases in the MPU-9255
00589 // Are we handling the temperature correction bit properly?
00590 // Push accelerometer biases to hardware registers
00591 /*  writeByte(MPU9255_ADDRESS, XA_OFFSET_H, data[0]);
00592   writeByte(MPU9255_ADDRESS, XA_OFFSET_L, data[1]);
00593   writeByte(MPU9255_ADDRESS, YA_OFFSET_H, data[2]);
00594   writeByte(MPU9255_ADDRESS, YA_OFFSET_L, data[3]);
00595   writeByte(MPU9255_ADDRESS, ZA_OFFSET_H, data[4]);
00596   writeByte(MPU9255_ADDRESS, ZA_OFFSET_L, data[5]);
00597 */
00598 // Output scaled accelerometer biases for manual subtraction in the main program
00599    dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; 
00600    dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
00601    dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
00602 }
00603 
00604 
00605 // Accelerometer and gyroscope self test; check calibration wrt factory settings
00606 void MPU9255SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
00607 {
00608    uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
00609    uint8_t selfTest[6];
00610     int32_t gAvg[3] = {0}, aAvg[3] = {0}, aSTAvg[3] = {0}, gSTAvg[3] = {0};
00611    float factoryTrim[6];
00612    uint8_t FS = 0;
00613    
00614   writeByte(MPU9255_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz
00615   writeByte(MPU9255_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
00616   writeByte(MPU9255_ADDRESS, GYRO_CONFIG, FS<<3); // Set full scale range for the gyro to 250 dps
00617   writeByte(MPU9255_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
00618   writeByte(MPU9255_ADDRESS, ACCEL_CONFIG, FS<<3); // Set full scale range for the accelerometer to 2 g
00619 
00620   for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer
00621   
00622   readBytes(MPU9255_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00623   aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00624   aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00625   aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00626   
00627     readBytes(MPU9255_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00628   gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00629   gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00630   gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00631   }
00632   
00633   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings
00634   aAvg[ii] /= 200;
00635   gAvg[ii] /= 200;
00636   }
00637   
00638 // Configure the accelerometer for self-test
00639    writeByte(MPU9255_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
00640    writeByte(MPU9255_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
00641    wait_ms(25); // wait_ms a while to let the device stabilize
00642 
00643   for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer
00644   
00645   readBytes(MPU9255_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00646   aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00647   aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00648   aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00649   
00650     readBytes(MPU9255_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00651   gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00652   gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00653   gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00654   }
00655   
00656   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings
00657   aSTAvg[ii] /= 200;
00658   gSTAvg[ii] /= 200;
00659   }
00660   
00661  // Configure the gyro and accelerometer for normal operation
00662    writeByte(MPU9255_ADDRESS, ACCEL_CONFIG, 0x00);
00663    writeByte(MPU9255_ADDRESS, GYRO_CONFIG, 0x00);
00664    wait_ms(25); // wait_ms a while to let the device stabilize
00665    
00666    // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
00667    selfTest[0] = readByte(MPU9255_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
00668    selfTest[1] = readByte(MPU9255_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
00669    selfTest[2] = readByte(MPU9255_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
00670    selfTest[3] = readByte(MPU9255_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results
00671    selfTest[4] = readByte(MPU9255_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results
00672    selfTest[5] = readByte(MPU9255_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results
00673 
00674   // Retrieve factory self-test value from self-test code reads
00675    factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
00676    factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
00677    factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
00678    factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
00679    factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
00680    factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation
00681  
00682  // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
00683  // To get percent, must multiply by 100
00684    for (int i = 0; i < 3; i++) {
00685      destination[i] = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i] - 100.; // Report percent differences
00686      destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3] - 100.; // Report percent differences
00687    }
00688    
00689 }
00690 
00691 
00692 
00693 // Implementation of Sebastian Madgwick's "...efficient orientation filter for... inertial/magnetic sensor arrays"
00694 // (see http://www.x-io.co.uk/category/open-source/ for examples and more details)
00695 // which fuses acceleration, rotation rate, and magnetic moments to produce a quaternion-based estimate of absolute
00696 // device orientation -- which can be converted to yaw, pitch, and roll. Useful for stabilizing quadcopters, etc.
00697 // The performance of the orientation filter is at least as good as conventional Kalman-based filtering algorithms
00698 // but is much less computationally intensive---it can be performed on a 3.3 V Pro Mini operating at 8 MHz!
00699         void MadgwickQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
00700         {
00701             float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
00702             float norm;
00703             float hx, hy, _2bx, _2bz;
00704             float s1, s2, s3, s4;
00705             float qDot1, qDot2, qDot3, qDot4;
00706 
00707             // Auxiliary variables to avoid repeated arithmetic
00708             float _2q1mx;
00709             float _2q1my;
00710             float _2q1mz;
00711             float _2q2mx;
00712             float _4bx;
00713             float _4bz;
00714             float _2q1 = 2.0f * q1;
00715             float _2q2 = 2.0f * q2;
00716             float _2q3 = 2.0f * q3;
00717             float _2q4 = 2.0f * q4;
00718             float _2q1q3 = 2.0f * q1 * q3;
00719             float _2q3q4 = 2.0f * q3 * q4;
00720             float q1q1 = q1 * q1;
00721             float q1q2 = q1 * q2;
00722             float q1q3 = q1 * q3;
00723             float q1q4 = q1 * q4;
00724             float q2q2 = q2 * q2;
00725             float q2q3 = q2 * q3;
00726             float q2q4 = q2 * q4;
00727             float q3q3 = q3 * q3;
00728             float q3q4 = q3 * q4;
00729             float q4q4 = q4 * q4;
00730 
00731             // Normalise accelerometer measurement
00732             norm = sqrt(ax * ax + ay * ay + az * az);
00733             if (norm == 0.0f) return; // handle NaN
00734             norm = 1.0f/norm;
00735             ax *= norm;
00736             ay *= norm;
00737             az *= norm;
00738 
00739             // Normalise magnetometer measurement
00740             norm = sqrt(mx * mx + my * my + mz * mz);
00741             if (norm == 0.0f) return; // handle NaN
00742             norm = 1.0f/norm;
00743             mx *= norm;
00744             my *= norm;
00745             mz *= norm;
00746 
00747             // Reference direction of Earth's magnetic field
00748             _2q1mx = 2.0f * q1 * mx;
00749             _2q1my = 2.0f * q1 * my;
00750             _2q1mz = 2.0f * q1 * mz;
00751             _2q2mx = 2.0f * q2 * mx;
00752             hx = mx * q1q1 - _2q1my * q4 + _2q1mz * q3 + mx * q2q2 + _2q2 * my * q3 + _2q2 * mz * q4 - mx * q3q3 - mx * q4q4;
00753             hy = _2q1mx * q4 + my * q1q1 - _2q1mz * q2 + _2q2mx * q3 - my * q2q2 + my * q3q3 + _2q3 * mz * q4 - my * q4q4;
00754             _2bx = sqrt(hx * hx + hy * hy);
00755             _2bz = -_2q1mx * q3 + _2q1my * q2 + mz * q1q1 + _2q2mx * q4 - mz * q2q2 + _2q3 * my * q4 - mz * q3q3 + mz * q4q4;
00756             _4bx = 2.0f * _2bx;
00757             _4bz = 2.0f * _2bz;
00758 
00759             // Gradient decent algorithm corrective step
00760             s1 = -_2q3 * (2.0f * q2q4 - _2q1q3 - ax) + _2q2 * (2.0f * q1q2 + _2q3q4 - ay) - _2bz * q3 * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (-_2bx * q4 + _2bz * q2) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + _2bx * q3 * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
00761             s2 = _2q4 * (2.0f * q2q4 - _2q1q3 - ax) + _2q1 * (2.0f * q1q2 + _2q3q4 - ay) - 4.0f * q2 * (1.0f - 2.0f * q2q2 - 2.0f * q3q3 - az) + _2bz * q4 * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (_2bx * q3 + _2bz * q1) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + (_2bx * q4 - _4bz * q2) * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
00762             s3 = -_2q1 * (2.0f * q2q4 - _2q1q3 - ax) + _2q4 * (2.0f * q1q2 + _2q3q4 - ay) - 4.0f * q3 * (1.0f - 2.0f * q2q2 - 2.0f * q3q3 - az) + (-_4bx * q3 - _2bz * q1) * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (_2bx * q2 + _2bz * q4) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + (_2bx * q1 - _4bz * q3) * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
00763             s4 = _2q2 * (2.0f * q2q4 - _2q1q3 - ax) + _2q3 * (2.0f * q1q2 + _2q3q4 - ay) + (-_4bx * q4 + _2bz * q2) * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (-_2bx * q1 + _2bz * q3) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + _2bx * q2 * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
00764             norm = sqrt(s1 * s1 + s2 * s2 + s3 * s3 + s4 * s4);    // normalise step magnitude
00765             norm = 1.0f/norm;
00766             s1 *= norm;
00767             s2 *= norm;
00768             s3 *= norm;
00769             s4 *= norm;
00770 
00771             // Compute rate of change of quaternion
00772             qDot1 = 0.5f * (-q2 * gx - q3 * gy - q4 * gz) - beta * s1;
00773             qDot2 = 0.5f * (q1 * gx + q3 * gz - q4 * gy) - beta * s2;
00774             qDot3 = 0.5f * (q1 * gy - q2 * gz + q4 * gx) - beta * s3;
00775             qDot4 = 0.5f * (q1 * gz + q2 * gy - q3 * gx) - beta * s4;
00776 
00777             // Integrate to yield quaternion
00778             q1 += qDot1 * deltat;
00779             q2 += qDot2 * deltat;
00780             q3 += qDot3 * deltat;
00781             q4 += qDot4 * deltat;
00782             norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);    // normalise quaternion
00783             norm = 1.0f/norm;
00784             q[0] = q1 * norm;
00785             q[1] = q2 * norm;
00786             q[2] = q3 * norm;
00787             q[3] = q4 * norm;
00788 
00789         }
00790   
00791   
00792   
00793  // Similar to Madgwick scheme but uses proportional and integral filtering on the error between estimated reference vectors and
00794  // measured ones. 
00795             void MahonyQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
00796         {
00797             float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
00798             float norm;
00799             float hx, hy, bx, bz;
00800             float vx, vy, vz, wx, wy, wz;
00801             float ex, ey, ez;
00802             float pa, pb, pc;
00803 
00804             // Auxiliary variables to avoid repeated arithmetic
00805             float q1q1 = q1 * q1;
00806             float q1q2 = q1 * q2;
00807             float q1q3 = q1 * q3;
00808             float q1q4 = q1 * q4;
00809             float q2q2 = q2 * q2;
00810             float q2q3 = q2 * q3;
00811             float q2q4 = q2 * q4;
00812             float q3q3 = q3 * q3;
00813             float q3q4 = q3 * q4;
00814             float q4q4 = q4 * q4;   
00815 
00816             // Normalise accelerometer measurement
00817             norm = sqrt(ax * ax + ay * ay + az * az);
00818             if (norm == 0.0f) return; // handle NaN
00819             norm = 1.0f / norm;        // use reciprocal for division
00820             ax *= norm;
00821             ay *= norm;
00822             az *= norm;
00823 
00824             // Normalise magnetometer measurement
00825             norm = sqrt(mx * mx + my * my + mz * mz);
00826             if (norm == 0.0f) return; // handle NaN
00827             norm = 1.0f / norm;        // use reciprocal for division
00828             mx *= norm;
00829             my *= norm;
00830             mz *= norm;
00831 
00832             // Reference direction of Earth's magnetic field
00833             hx = 2.0f * mx * (0.5f - q3q3 - q4q4) + 2.0f * my * (q2q3 - q1q4) + 2.0f * mz * (q2q4 + q1q3);
00834             hy = 2.0f * mx * (q2q3 + q1q4) + 2.0f * my * (0.5f - q2q2 - q4q4) + 2.0f * mz * (q3q4 - q1q2);
00835             bx = sqrt((hx * hx) + (hy * hy));
00836             bz = 2.0f * mx * (q2q4 - q1q3) + 2.0f * my * (q3q4 + q1q2) + 2.0f * mz * (0.5f - q2q2 - q3q3);
00837 
00838             // Estimated direction of gravity and magnetic field
00839             vx = 2.0f * (q2q4 - q1q3);
00840             vy = 2.0f * (q1q2 + q3q4);
00841             vz = q1q1 - q2q2 - q3q3 + q4q4;
00842             wx = 2.0f * bx * (0.5f - q3q3 - q4q4) + 2.0f * bz * (q2q4 - q1q3);
00843             wy = 2.0f * bx * (q2q3 - q1q4) + 2.0f * bz * (q1q2 + q3q4);
00844             wz = 2.0f * bx * (q1q3 + q2q4) + 2.0f * bz * (0.5f - q2q2 - q3q3);  
00845 
00846             // Error is cross product between estimated direction and measured direction of gravity
00847             ex = (ay * vz - az * vy) + (my * wz - mz * wy);
00848             ey = (az * vx - ax * vz) + (mz * wx - mx * wz);
00849             ez = (ax * vy - ay * vx) + (mx * wy - my * wx);
00850             if (Ki > 0.0f)
00851             {
00852                 eInt[0] += ex;      // accumulate integral error
00853                 eInt[1] += ey;
00854                 eInt[2] += ez;
00855             }
00856             else
00857             {
00858                 eInt[0] = 0.0f;     // prevent integral wind up
00859                 eInt[1] = 0.0f;
00860                 eInt[2] = 0.0f;
00861             }
00862 
00863             // Apply feedback terms
00864             gx = gx + Kp * ex + Ki * eInt[0];
00865             gy = gy + Kp * ey + Ki * eInt[1];
00866             gz = gz + Kp * ez + Ki * eInt[2];
00867 
00868             // Integrate rate of change of quaternion
00869             pa = q2;
00870             pb = q3;
00871             pc = q4;
00872             q1 = q1 + (-q2 * gx - q3 * gy - q4 * gz) * (0.5f * deltat);
00873             q2 = pa + (q1 * gx + pb * gz - pc * gy) * (0.5f * deltat);
00874             q3 = pb + (q1 * gy - pa * gz + pc * gx) * (0.5f * deltat);
00875             q4 = pc + (q1 * gz + pa * gy - pb * gx) * (0.5f * deltat);
00876 
00877             // Normalise quaternion
00878             norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);
00879             norm = 1.0f / norm;
00880             q[0] = q1 * norm;
00881             q[1] = q2 * norm;
00882             q[2] = q3 * norm;
00883             q[3] = q4 * norm;
00884  
00885         }
00886   };
00887 #endif